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Research Papers

# Investigation of Street Lamp With Automatic Solar Tracking SystemPUBLIC ACCESS

[+] Author and Article Information
Siyuan Lu, Rong Dai

School of Mechanical Engineering,
Jiangsu University,
Zhenjiang 212013, China

Guangru Zhang

State Key Laboratory of Materials-Oriented
Chemical Engineering,
Nanjing Tech University,
Nanjing 210009, China

Quan Wang

School of Mechanical Engineering,
Jiangsu University,
Zhenjiang 212013, China;
State Key Laboratory of Transducer Technology,
Shanghai 200050, China
e-mail: wangq@mail.ujs.edu.cn

1Corresponding author.

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING: INCLUDING WIND ENERGY AND BUILDING ENERGY CONSERVATION. Manuscript received August 20, 2017; final manuscript received March 22, 2018; published online April 16, 2018. Assoc. Editor: Geoffrey T. Klise.

J. Sol. Energy Eng 140(6), 061002 (Apr 16, 2018) (7 pages) Paper No: SOL-17-1343; doi: 10.1115/1.4039776 History: Received August 20, 2017; Revised March 22, 2018

## Abstract

A street lamp with automatic solar tracking system can control the adjusting mechanism of azimuth and altitude so that the solar panel may adapt itself to the sunlight to improve the photoelectric conversion efficiency. In this work, we demonstrated the design of the adjusting mechanism of azimuth and altitude and verified the wind resistance. The method was realized by capturing the incident direction of sunlight using the photodiode array. The signal of the photodiode array can be processed by LM339N and then was sent to the single chip, which can deal with the signal to the motor of the adjusting mechanism of azimuth and the linear actuator of the adjusting mechanism of altitude, respectively. The hall sensors, embedded in the adjusting mechanism, are utilized to fulfill the feedback of the motion position to the single chip. These results clearly reveal the potential of the system in application.

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## Introduction

Solar street lamps have been widely used. They have many merits such as high reliability and long life, and little manual intervention is required. In addition, a solar street lamp does not need wiring–building. It can be installed conveniently and contributes to reduce the pavement damage. The energy is clean, so it can also achieve the purpose of energy saving and emission reduction.

However, a solar street lamp also has many shortcomings. One of the most glaring is that the photoelectric conversion efficiency of a solar cell panel is lower and the common photoelectric conversion efficiency of a solar cell panel is generally only between 10% and 15%. As the solar energy itself is not very stable, it is greatly affected by weather and has unsolvable intermittent problems [1]. It is greatly affected by light conditions. The energy source of a solar street lamp only depends on solar energy, while the low photoelectric conversion efficiency and the instability of solar energy have also limited the energy supply for a solar street lamp. Therefore, improving the photoelectric conversion efficiency of the solar panel or using the large-area solar panel is an important way to encourage solar street lamps to work properly.

Although enlarging the area of the solar panel can improve the daily generating capacity, it needs to increase the wind resistance performance of the lamp holder. This is because the solar panel is generally installed on the top of the street lamp. After enlarging the area of a solar panel, the effects of wind force will be significantly heightened. In addition, on account of the higher cost of a solar panel, using a large panel needs to increase the cost of the solar panel materials and the cost of improving the wind resistance performance of the lamp holder.

Improving the photoelectric conversion efficiency of a solar panel is another way to increase the daily generating capacity of it. Mohammad and Karim [2] proposed that dual-axis tracking system can produce 18% extra solar energy when compared with a single-axis tracking system, while the hybrid tracking system can supply more energy than the dual-axis one. It is indicated that the implementation of solar tracking system in photovoltaic system is an important way to improve its efficiency [3]. But using more axes in tracking system may increase the cost [4]. Wentzel and Pouris [5] launched a solar tracking device, which converted the optical signal into MCU (Micro-controller unit) through the optical sensor and the photoelectric detection circuit. After processing the electrical signal, MCU outputs the control signal to operate the motor in order to accomplish the tracking. Based on the shape memory alloy controller, Ibrahim et al. [6] achieved the single-axis passive sun tracking through the temperature variation generated by sunlight. Rao et al. [7] developed a two-dimensional programmable solar tracker control system. It defined the motion mathematical model of the solar tracker by the analysis and research of the sun motion path theory and obtained the sun tracking through the microcomputer remote controlling. Zhao and Bi [8] designed the full-automatic portable solar radiometer based on the complementary metal oxide semiconductor image sensor ADC-2121 (Agilent Technologies Co., Ltd, Santa Clara, CA). This method had the advantages of high precision, being free to settle zero and so on. Wang et al. [9] proposed a sun tracker based on a position sensitive detector. It had been proved that the sun tracker could achieve the desired performance index.

However, Bakhshi and Sadeh [10] held their views that solar trackers may not be economic, although they can capture more solar energy when used in photovoltaic systems. Eldin et al. [11] put forward that it could be more effective to use the solar trackers in cold regions than in hot regions, because the latter one could have more sufficient solar irradiance.

Overcoming the deficiencies of the predecessors, we present a new way with automatic tracking the incident direction of sunlight to improve the photoelectric conversion efficiency of solar cell panels. This kind of method can keep the solar panel vertical to the incident direction of sunlight at any time in order to absorb more solar energy and can go up the photoelectric conversion efficiency of the solar panel by 20–25%. Besides, we cut down the price of the solar tracker by our design.

The function of the adjusting mechanism is to receive the control signal from MCU to manipulate the solar panel so as to keep it vertical to the incident direction of sunlight. Alexandru [12] proposed two ways to design the tracking systems, which are by one axis and by two axes. Compared with one-axis tracking systems, two-axes tracking systems show their excellent performance in tracking the sun. Seme et al. [13] showed two different implementations of two axes trackers: tip-tilt trackers and azimuth-altitude trackers. For achieving more precise tracking effects, we choose two-axes tracking system and use the azimuth-altitude tracker as the form of the system. So, the design of the adjusting mechanism is divided into two parts as an azimuth adjusting mechanism and an altitude adjusting mechanism. The azimuth adjusting mechanism is to change the angle of a solar panel on the horizontal plane so that the solar panel turns to the maximum direction of sunlight intensity. The altitude adjusting mechanism is to change the elevation of the solar panel so that the solar panel turns to the maximum height of sunlight intensity.

Figure 1 depicts the azimuth adjusting mechanism. It handles torque through the DC geared motor and transfers the output torque to the twisting hollow shaft through the rigid coupling. It is fixed by a pair of tapered roller bearings and has a hinge bracket on the top for connecting the solar panel.

Figure 2 illustrates the altitude angle adjustment mechanism. In the mechanism, the second hinge base is connected with the moving rod of the electric drive pusher and the solar panel. The elevation of the solar panel is changed with the electric drive pusher telescoping.

The motor of the azimuth adjusting mechanism is the DC geared motor. It needs to be checked in the negative torque generated by the wind force acting directly on the motor, which may bring about the damage of the motor.

Figure 3 illustrates the bearing wind load diagrammatic drawing of the azimuth adjusting mechanism under the theory state. When the elevation of the solar panel is minimum, the effective area of the wind force acting on the solar panel in horizontal direction is maximum. Hence, the influence of the azimuth adjusting mechanism bearing wind force is also maximum at the same time.

Provided that the wind force would entirely act on the right-half plane of a solar panel, as shown in the shaded area of Fig. 3, the negative torque for the wind force producing is maximum. The dynamic pressure formula of wind is Display Formula

(1)$Pb=12ρV2$

where ρ is the density of air as ρ = 1.29 kg/m3, V is the wind speed, taken the wind speed of whole gale as V = 28.40 m/s. After calculating, the dynamic pressure of wind has Pb = 520.23 N/m2.

The negative torque generated by the wind force acting on the right-half plane of a solar panel is Display Formula

(2)$T=∫0ax⋅Pb⋅h⋅dx$

where a is half of the solar panel width with as 0.32 m, h is the effective height of the solar panel under wind force load as 0.50 m, and Pb = 520.23 N/m2. The calculated negative torque is 13.32 N·m and the rated torque of the motor is 13.8 N·m. Therefore, the azimuth adjusting mechanism can resist at least the whole gale.

## Detecting the Direction and Height of Sunlight

We perform a photodiode array to detect the direction and height of sunlight, shown in Fig. 4. D1D7 are photodiodes and their distribution is on a spherical surface. D3D7 are used for detecting the direction of sunlight and measuring the intensity of sunlight in five directions. D1, D5, and D2 are used for detecting the height of sunlight and measuring the intensity of sunlight in three altitudes, respectively [14].

Figure 5 describes a photodiode array connection. The negative electrodes of photodiodes are connected to the negative electrode of a power source and the positive electrodes of photodiodes are connected to the positive electrode of a power source through a 10 kΩ resistance [15]. The negative electrode of each photodiode is used as the output signal of the photodiode array and their output signals are V1V7. According to the characteristics of the photodiode, when sunlight enters the photodiode, it can generate photocurrent and with the sunlight intensity enhancing, the photocurrent also increases gradually within a certain range. With each photodiode being series connection with the corresponding resistance, the voltage drop of the resistance increases to decrease the potential of the negative electrode of the photodiode when the photocurrent increases. Hence, V1V7 are analog signals and their values are concerned with the sunlight intensity entering into the photodiodes.

Using voltage comparison chip LM339N is to make comparisons to output signals from the photodiode array. Figure 6 depicts LM339N and the photodiode array connection. It uses four LM339N chips and each of them has four independent voltage comparators for making comparisons to 16 couples of potential values, and then outputs the compared results in the form of a digital signal. The output signals of LM339N are transmitted to MCU for processing. According to the connection method shown in Fig. 6, Table 1 is the logic signals of I/O ports corresponding to MCU accessing the minimum value from V1, V5, and V2. Table 2 is the logic signals of I/O ports corresponding to MCU accessing the minimum from V3 to V7 and X is 0 or 1 in the table. MCU reads the corresponding I/O ports and then obtains the minimum of V3V7 and the minimum of V1, V5, and V2. The position of the photodiode corresponding to the minimum of V3V7 is the direction of sunlight and the position of the photodiode corresponding to the minimum of V1, V5, and V2 is the height of sunlight.

## Automatic Tracking System

According to the collections of the sunlight's direction and height, the automatic tracking system outputs control signals to the adjusting mechanism. Meanwhile, the control system collects the motion and position information that hall sensors on the adjusting mechanism feedback to form a closed-loop control so that the direction of a solar panel can be precisely adjusted to be always keeping it vertical to the incident direction of sunlight.

As shown in Fig. 7, it is a distribution schematic drawing of hall sensors in the azimuth adjustment mechanism. The magnet turns with the rigid coupling on which it is mounted. When the magnet approaches to one of hall sensors, the hall sensor will generate an induction signal into MCU so as to obtain the motion position of the azimuth adjusting mechanism. Hall sensors in the altitude adjustment mechanism are distributed in an electric drive pusher. The number of them is altogether three, respectively, installed on the middle and both ends of the telescopic cylinder of the electric drive pusher. A magnet is fixed on the telescopic rod of the electric drive pusher. When the electric drive pusher moves to the bottom, the middle, and the end, the hall sensor matched with each position will output an induction signal into MCU so as to obtain the motion position of the altitude adjusting mechanism.

## Day and Night Identification Circuit

The day and night identification circuit makes use of the photo resistance to collect the environmental sunlight intensity and then makes use of Wheatstone bridge and LM339N to process its output signal [18]. As shown in Fig. 9, it is a day and night identification circuit module diagram. The Rx is a photo resistance and its resistance value will be affected by sunlight intensity.

When the environmental sunlight intensity is larger, it is identified for daytime state. The resistance value of the photo resistance is smaller. The potential value of the upper bridge arm midpoint of Wheatstone bridge is larger than the potential value of the lower bridge arm midpoint of Wheatstone bridge. LM339N no. 2 pin outputs a logic signal 0 into the MCU P3.3 port. When the environmental sunlight intensity is smaller, it is identified for nighttime state. The resistance value of the photo resistance is larger. The potential value of the upper bridge arm midpoint of Wheatstone bridge is smaller than the potential value of the lower bridge arm midpoint of Wheatstone bridge. LM339N no. 2 pin outputs a logic signal 1 into the MCU P3.3 port [1921].

The balance equation of Wheatstone bridge is Display Formula

(3)$Rx⋅R3=R1⋅R2$

To make no. 2 pin of LM339N output a logic signal 1, namely, nighttime state, the following in equation must be satisfied Display Formula

(4)$Rx⋅R3>R1⋅R2$

Under the condition of the values of R1 and R2 being unchanged, if R3 is smaller, the need of environmental sunlight intensity will become very small and only when the value of Rx is larger, it can make the inequation above established. On the contrary, if R3 is larger, the environmental sunlight intensity does not need to be very small, namely, Rx without a larger value can also make the inequation above established. Therefore, choosing different values of R3 can set the sunlight intensity needed to make the relative value of the bridge arm midpoint potential changed, namely, it can set the sunlight intensity needed to make the day and night identification circuit occur response.

Figure 10 describes an MCU executive program flow chart. MCU scans P3.3 port once in a working cycle to determine whether the environmental sunlight intensity is less than the setting value. If so, the street lamp illuminating is turned on. Figure 11 is a real solar street lamp photo with automatic tracking sunlight incident direction. In the test, the street lamp can be stably operated, and can realize the functions for automatic tracking the sunlight incident direction and automatically turning on the street lamp.

## Conclusion

The solar street lamp system with automatic tracking sunlight incident direction utilizes the photodiode array to collect the direction and height of sunlight and controls the motion of the adjustment mechanism to keep the solar panel vertical to the sunlight incident direction so that the photoelectric conversion efficiency of a solar panel can be raised to further improve the usability of the street lamp. The adjusting mechanism of the street lamp used for adjusting the solar panel direction can be reasonably integrated with the lamp holder. Hence, there is excellent practicability and stability and can resist at least the wind force of whole gale in the outer environment. What was designed, such as the direction and height detection circuit of sunlight, the motor drive control circuit, the day and night identification module circuit, and so on, are simple and efficient, and can ensure that the signal collection and the control execution are absolutely precise.

## Funding Data

• National Natural Science Foundation of China (Grant Nos. 51675246 and 91750112).

• Zhenjiang Science & Technology Program (Grant No. GY2015023).

• State Key Laboratory of Materials-Oriented Chemical Engineering (Grant No. GY KL16-10).

## References

Regattieri, A. , Piana, F. , Bortolini, M. , Gamberi, M. , and Ferrari, E. , 2016, “ Innovative Portable Solar Cooker Using the Packaging Waste of Humanitarian Supplies,” Renew. Sust. Energ. Rev., 57, pp. 319–326.
Mohammad, N. , and Karim, T. , 2013, “ Design and Implementation of Hybrid Automatic Solar-Tracking System,” ASME J. Sol. Energy Eng., 135(1), p. 011013.
Zhang, Q. X. , Yu, Y. H. , Zhang, Q. Y. , Zhang, Z. Y. , Shao, C. H. , and Yang, D. , 2015, “ A Solar Automatic Tracking System That Generates Power for Lighting Greenhouses,” Energies, 8(7), pp. 7367–7380.
Abu-Malouh, R. , Abdallah, S. , and Muslih, I. M. , 2010, “ Design, Construction and Operation of Spherical Solar Cooker With Automatic Sun Tracking System,” Energy Convers. Manage., 52(1), pp. 615–620.
Wentzel, M. , and Pouris, A. , 2007, “ The Development Impact of Solar Cooker: A Review of Solar Cooking Impact Research in South Africa,” Energy Policy, 35(3), pp. 1909–1919.
Lbrahim, S. , Demirtas, M. , and Llhami, C. , 2009, “ Application of One-Axis Sun Tracking System,” Energy Convers. Manage., 50(11), pp. 2709–2718.
Rao, P. , Sun, S. L. , and Ye, H. Y. , 2004, “ Development of Two Dimensional Program Control Solar Tracker Control System,” Control Eng., 11(6), pp. 542–545 (in Chinese).
Zhao, Z. G. , and Bi, X. L. , 2006, “ Application of CMOS Image Sensor in Photoelectric Automatic Tracking System,” Sci. Technol. Eng., 6(3), pp. 312–314 (in Chinese).
Wang, Z. C. , Han, D. , Xu, G. L. , Mao, J. G. , and Shen, H. , 2009, “ Design of New Sun-Tracking Device,” Transducer Microsyst. Technol., 28(2), pp. 91–93 (in Chinese).
Bakhshi, R. , and Sadeh, J. , 2016, “ A Comprehensive Economic Analysis Method for Selecting the PV Array Structure in Grid–Connected Photovoltaic Systems,” Renewable Energy, 94, pp. 524–536.
Eldin, S. A. S. , Abd-Elhady, M. S. , and Kandil, H. A. , 2015, “ Feasibility of Solar Tracking Systems for PV Panels in Hot and Cold Regions,” Renewable Energy, 85, pp. 228–233.
Alexandru, C. , 2013, “ A Novel Open-Loop Tracking Strategy for Photovoltaic Systems,” Sci. World J., 2013(2013), p. 205396.
Seme, S. , Štumberger, B. , and Hadžiselimović, M. , 2016, “ A Novel Prediction Algorithm for Solar Angles Using Second Derivative of the Energy for Photovoltaic Sun Tracking Purposes,” Sol. Energy, 137, pp. 201–211.
Wang, Q. , Zhang, J. , Hu, R. , and Shao, Y. , 2010, “ Automatic Two Axes Sun-Tracking System Applied to Photovoltaic System for LED Street Light,” Appl. Mech. Mater., 43, pp. 17–20.
Zhang, L. L. , and Wang, J. M. , 2010, “ Implementation of the Sun's Position Photoelectricity Analog Signal Detecting and Tracking,” Tech. Autom. Appl., 29(9), pp. 40–43 (in Chinese).
Çinar, S. M. , Hocaoğlu, F. O. , and Orhun, M. , 2014, “ A Remotely Accessible Solar Tracker System Design,” J. Renewable Sustainable Energy, 6(3), pp. 278–287.
Betin, F. , Pinchon, D. , and Capolino, G. A. , 2002, “ A Time-Varying Sliding Surface for Robust Position Control of a DC Motor Drive,” IEEE Trans. Ind. Electron., 49(2), pp. 462–473.
Singh, G. K. , 2013, “ Solar Power Generation by PV (Photovoltaic) Technology: A Review,” Energy, 53, pp. 1–13.
Lee, Y. P. , Chen, S. H. , Gau, Y. Q. , Wang, K. D. , Ma, S. H. , and Wu, J. H. , 2012, “ Analysis and Design of a Single-Axis Automatic Solar Tracking and Power Filtering System for Solar Power Generation,” Sensor Lett., 10(5), pp. 1075–1080.
Mousazadeh, H. , Keyhania, A. , Javadi, A. , Mobli, H. , Abriniac, K. , and Sharifi, A. , 2009, “ A Review of Principle and Sun-Tracking Methods for Maximizing Solar Systems Output,” Renewable Sustainable Energy Rev., 13(8), pp. 1800–1818.
Abdallah, E. , Akayleh, A. , Abdallah, S. , and Hrayshat, E. S. , 2009, “ A Parabolic Solar Cooker With Automatic Two Axes Sun Tracking System,” Appl. Energy, 87(2), pp. 463–470.
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## References

Regattieri, A. , Piana, F. , Bortolini, M. , Gamberi, M. , and Ferrari, E. , 2016, “ Innovative Portable Solar Cooker Using the Packaging Waste of Humanitarian Supplies,” Renew. Sust. Energ. Rev., 57, pp. 319–326.
Mohammad, N. , and Karim, T. , 2013, “ Design and Implementation of Hybrid Automatic Solar-Tracking System,” ASME J. Sol. Energy Eng., 135(1), p. 011013.
Zhang, Q. X. , Yu, Y. H. , Zhang, Q. Y. , Zhang, Z. Y. , Shao, C. H. , and Yang, D. , 2015, “ A Solar Automatic Tracking System That Generates Power for Lighting Greenhouses,” Energies, 8(7), pp. 7367–7380.
Abu-Malouh, R. , Abdallah, S. , and Muslih, I. M. , 2010, “ Design, Construction and Operation of Spherical Solar Cooker With Automatic Sun Tracking System,” Energy Convers. Manage., 52(1), pp. 615–620.
Wentzel, M. , and Pouris, A. , 2007, “ The Development Impact of Solar Cooker: A Review of Solar Cooking Impact Research in South Africa,” Energy Policy, 35(3), pp. 1909–1919.
Lbrahim, S. , Demirtas, M. , and Llhami, C. , 2009, “ Application of One-Axis Sun Tracking System,” Energy Convers. Manage., 50(11), pp. 2709–2718.
Rao, P. , Sun, S. L. , and Ye, H. Y. , 2004, “ Development of Two Dimensional Program Control Solar Tracker Control System,” Control Eng., 11(6), pp. 542–545 (in Chinese).
Zhao, Z. G. , and Bi, X. L. , 2006, “ Application of CMOS Image Sensor in Photoelectric Automatic Tracking System,” Sci. Technol. Eng., 6(3), pp. 312–314 (in Chinese).
Wang, Z. C. , Han, D. , Xu, G. L. , Mao, J. G. , and Shen, H. , 2009, “ Design of New Sun-Tracking Device,” Transducer Microsyst. Technol., 28(2), pp. 91–93 (in Chinese).
Bakhshi, R. , and Sadeh, J. , 2016, “ A Comprehensive Economic Analysis Method for Selecting the PV Array Structure in Grid–Connected Photovoltaic Systems,” Renewable Energy, 94, pp. 524–536.
Eldin, S. A. S. , Abd-Elhady, M. S. , and Kandil, H. A. , 2015, “ Feasibility of Solar Tracking Systems for PV Panels in Hot and Cold Regions,” Renewable Energy, 85, pp. 228–233.
Alexandru, C. , 2013, “ A Novel Open-Loop Tracking Strategy for Photovoltaic Systems,” Sci. World J., 2013(2013), p. 205396.
Seme, S. , Štumberger, B. , and Hadžiselimović, M. , 2016, “ A Novel Prediction Algorithm for Solar Angles Using Second Derivative of the Energy for Photovoltaic Sun Tracking Purposes,” Sol. Energy, 137, pp. 201–211.
Wang, Q. , Zhang, J. , Hu, R. , and Shao, Y. , 2010, “ Automatic Two Axes Sun-Tracking System Applied to Photovoltaic System for LED Street Light,” Appl. Mech. Mater., 43, pp. 17–20.
Zhang, L. L. , and Wang, J. M. , 2010, “ Implementation of the Sun's Position Photoelectricity Analog Signal Detecting and Tracking,” Tech. Autom. Appl., 29(9), pp. 40–43 (in Chinese).
Çinar, S. M. , Hocaoğlu, F. O. , and Orhun, M. , 2014, “ A Remotely Accessible Solar Tracker System Design,” J. Renewable Sustainable Energy, 6(3), pp. 278–287.
Betin, F. , Pinchon, D. , and Capolino, G. A. , 2002, “ A Time-Varying Sliding Surface for Robust Position Control of a DC Motor Drive,” IEEE Trans. Ind. Electron., 49(2), pp. 462–473.
Singh, G. K. , 2013, “ Solar Power Generation by PV (Photovoltaic) Technology: A Review,” Energy, 53, pp. 1–13.
Lee, Y. P. , Chen, S. H. , Gau, Y. Q. , Wang, K. D. , Ma, S. H. , and Wu, J. H. , 2012, “ Analysis and Design of a Single-Axis Automatic Solar Tracking and Power Filtering System for Solar Power Generation,” Sensor Lett., 10(5), pp. 1075–1080.
Mousazadeh, H. , Keyhania, A. , Javadi, A. , Mobli, H. , Abriniac, K. , and Sharifi, A. , 2009, “ A Review of Principle and Sun-Tracking Methods for Maximizing Solar Systems Output,” Renewable Sustainable Energy Rev., 13(8), pp. 1800–1818.
Abdallah, E. , Akayleh, A. , Abdallah, S. , and Hrayshat, E. S. , 2009, “ A Parabolic Solar Cooker With Automatic Two Axes Sun Tracking System,” Appl. Energy, 87(2), pp. 463–470.

## Figures

Fig. 1

Schematic diagram of the azimuth adjusting mechanism: (1) the first hinge mount, (2) magnet, (3) sensor bracket, (4) screw, (5) DC geared motor, (6) lamp holder, (7) motor fixed plate, (8) connecting pipe, (9) rigid coupling, (10) the first tapered roller bearing, (11) stationary cylinder, (12) the second tapered roller bearing, (13) the first cover of weatherproof, (14) the second cover of weather-proof, (15) twisting hollow shaft, (16) hinge bracket, and (17) top cover

Fig. 2

Schematic diagram of the altitude adjusting mechanism: (1) electric drive pusher, (2) solar panel, and (3) the second hinge bracket

Fig. 3

Fig. 4

Photodiode array diagrammatic drawing

Fig. 5

Photodiode array connection diagram

Fig. 6

LM339N and photodiode array connection diagrams

Fig. 7

Hall sensors distribution schematic drawing in the azimuth adjustment mechanism: (1) magnet, (2) rigid coupling, (3) hall sensor a, (4) hall sensor b, (5) hall sensor c, (6) hall sensor d, and (7) hall sensor e

Fig. 8

Schematic diagram showing motor drive circuit

Fig. 9

Schematic of day and night identification circuit module

Fig. 10

MCU executive program flowchart

Fig. 11

Photo of solar street lamp with automatic tracking sunlight incident direction

## Tables

Table 1 Logic signals of MCU I/O ports corresponding to the minimum of V1, V5, and V2
Table 2 Logic signals of MCU I/O ports corresponding to the minimum of V3V7

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